Dental plaque is a biofilm that adheres to tooth and other oral surfaces, particularly at the gingival margin, and is implicated in the occurrence of gingivitis, periodontitis, caries and other forms of periodontal disease. Various antibacterial agents can retard the growth of bacteria and thus reduce the formation of biofilm on oral surfaces. Zinc salts have been previously used as antibacterial agents. Without being bound by any theory, free zinc ions are believed to provide antibacterial efficacy by inhibition of glucose metabolism and/or interaction with the bacterial cell wall, reducing bacterial colonization of the oral cavity (as discussed in Cummins D., J. Clin. Periodontol. 1991; 18; 455-461). An insoluble zinc compound, zinc oxide, could also deliver strong antibacterial efficacy during tooth brushing. However, soluble zinc salts, such as zinc citrate, may react with calcium carbonate to form insoluble zinc carbonate, thus reducing the amount of zinc ions available for delivery to the tooth surface. Some consumers, however, prefer dentifrice compositions comprising a calcium carbonate abrasive (rather than a silica abrasive) due to their high cleaning efficacy. Calcium carbonate abrasives may also provide a cost advantage as compared to other types of abrasive.
It would therefore be desirable to provide an oral care composition which comprises a calcium carbonate abrasive, but which also maintains the high antibacterial and biofilm reduction efficacy of zinc salts present in the composition.